The username is only truncated if you are linked to a Microsoft Account. So, the easy solution to this problem is to unlink the Microsoft Account, when prompted for a username enter the full username you wish to use. Once you logout of the profile and log back into the profile, the user's profile directory, will reflect the name you entered in the prompt.

Understanding the Context

At that point you can link the user to ... TikTok says its security team is addressing an issue that allowed hackers to target several high-profile celebrity and brand accounts on its video platform, including those belonging to Paris Hilton, ... The social media platform TikTok has confirmed that high-profile accounts are being exploited and hijacked by threat actors in a takeover campaign. The threat was first discovered by Forbes on June 4, ...

Key Insights

Over the past week, attackers have hijacked high-profile TikTok accounts belonging to multiple companies and celebrities, exploiting a zero-day vulnerability in the social media's direct messages ...